03 Mini heat problem

[Janelle]

Hi! I'm brand new here. I LOVE my BRIGHT yellow cooper. I got it at auction from somebody who wanted it to look like an S, but it's not. My heat monitor has pegged out a couple of times. Sometimes it comes down, and then back up, and then stays up. While I can see no leaks (used cardboard underneath). Have added fluid a few times. Also, when it is HOT, the cabin is cold.. When I add a little fluid, the cabin heater works again, and it goes back to midpoint.


HELP?

[bad venge]

I'd check/replace thermostat first